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	<script type="text/javascript">
		var a = "This is a pig";	//有引号，字符串
		var b = "传智播客";			//有引号，字符串
		var c = "123123";			//有引号，字符串
		var d = "哈";				//有引号，字符串
		var e = "";					//有引号，字符串

		console.log(typeof a);      // string
		console.log(typeof b);      // string
		console.log(typeof c);      // string
		console.log(typeof d);      // string
		console.log(typeof e);      // string
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